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Nestle USA, Inc.—Ripon, CA January 28, 2011 <br /> 2011 Revised Feasibility Study <br /> including discharges of CDCs from the City of Ripon WWTP and/or <br /> discharges of CDCs from the City of Ripon sewer main. <br /> 3. The Corcoran Clay is a major regional aquitard beneath the Study <br /> Area. It has an average thickness of approximately 15 feet and slopes <br /> to the west. Increasing vertical gradients across the Corcoran Clay <br /> have been observed since approximately 2000, which will increase the <br /> rate of COCs input via conduit wells into the Lower Aquifer. <br /> 4. The B-Zone is primarily impacted by offsite historical leaks from the <br /> industrial sewer at offsite locations; onsite wells appear to be impacted <br /> by onsite releases. <br /> 5. The Upper Aquifer (A subzone) and Intermediate Aquifer are primarily <br /> affected by historical discharges from the City of Ripon WWTP <br /> lagoons. <br /> 6. Nestle's future groundwater remediation should focus on the Upper A- <br /> zone beneath the Site (approximately 50 to 80 feet bgs) where the <br /> highest TCE concentrations have been delineated. <br /> 7. Vertical conduit wells within the Study Area should be identified and <br /> properly decommissioned (see Figure 6). <br /> 8. Management of COC-affected groundwater should be a multi-party <br /> undertaking. Cooperation between Nestle, the City of Ripon, and other <br /> parties who influence groundwater migration patterns is needed to <br /> mitigate the migration of CDCs towards supply wells. <br /> 5 Remedial Action Objectives <br /> The Site RAOs are: <br /> 1. Restoration of groundwater to background conditions, to the extent <br /> technically and economically achievable, pursuant to State Water <br /> Resources Control Board Resolution Number 92-49X'X; <br /> 2. Prevent exposure of COCs at the Site to human receptors; and <br /> 3. Contain/capture the COCs in groundwater originating from the Site. <br /> There are no soil or air issues at the Site that require remedial action. <br /> Groundwater is the only media of concern. COCs in groundwater have driven <br /> the investigation and remediation efforts at the Site. TCE and its daughter <br /> products are the primary CDCs of greatest interest in groundwater. <br /> The focus of this 2011 Revised FS report is to address COCs present in <br /> groundwater within the Study Area. Addressing the areas of highest COC <br /> concentrations at the Site through containment and source removal appears to <br /> be feasible and will have the most benefit to groundwater restoration. An area of <br /> 10 <br />